SUMMARY
1. logical standby不支持cascading standby
2. 11.2.0.2之前版本cascading standby不支持RAC
3. 11.2.0.3之前版本DG Broker环境不支持cascaded standby
DETAILS
为了减少primary system负载,减少带宽需求,当需要配置多个standby时,可以采用cascade standby.
受支持的Cascading standby模式:
1. Primary DB > Physical Standby DB with cascaded destination > Physical Standby DB
2. Primary DB > Physical Standby DB with cascaded destination > Logical Standby DB
11.2.0.2之前,物理standby最多支持9个remote destination,11.2.0.2及之后最多支持30个。当物理standby配置了cascaded destination,在物理standby standby log满时或者归档后,将传输这些从primary接受的redo到第二个standby上。第二个standby与primary之间必定有lag存在。cascaded standby可用作非实时的报表系统。
配置Cascaded Destination
1.在standby创建standby redo logfile
2.在primary设定LOG_ARCHIVE_DEST_n参数,设定physical standby转发redo到cascaded destination.
定义传输模式:LGWR ASYNC或LGWR SYNC
设定VALID_FOR属性启用redo转发
3.转发redo的physical standby开启归档模式
4.配置转发redo的physical standby LOG_ARCHIVE_DEST_n参数
参数配置案例:
Boston Database (Primary Role):
DB_UNIQUE_NAME=boston
STANDBY_ARCHIVE_DEST=/arch1/boston/
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston,denver)'
LOG_ARCHIVE_DEST_1='LOCATION=/arch1/boston/ VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=boston'
LOG_ARCHIVE_DEST_2= 'SERVICE=denver VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=denver'
LOG_ARCHIVE_DEST_3='SERVICE=chicago VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=chicago'
Chicago Database (Standby Role):
DB_UNIQUE_NAME=chicago
LOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston,denver)'
STANDBY_ARCHIVE_DEST=/arch1/chicago/
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_DEST_1='LOCATION=/arch1/chicago/ VALID_FOR=(ONLINE_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=chicago'
LOG_ARCHIVE_DEST_2='SERVICE=denver VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=denver'
LOG_ARCHIVE_DEST_3='SERVICE=boston VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=boston'
Denver Database (Standby Role):
DB_UNIQUE_NAME=denver
LOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston,denver)'
STANDBY_ARCHIVE_DEST=/arch2/denver/ <====For Logical Standby
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_DEST_1='LOCATION=/arch1/denver/ VALID_FOR=(ONLINE_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=denver'
LOG_ARCHIVE_DEST_2='LOCATION=/arch2/denver/ VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=denver'
角色转变
Oracle建议主要用于灾难恢复的备份数据库直接接收重做数据从主数据库,数据保护可达到最佳水平。级联standby可以作防御的第二线,但其总是比primary延迟。